The neurological examination in the assessment of polyneuropathy in mechanically ventilated patients.

Polyneuropathy has been implicated in critical illness as a cause of difficult weaning from artificial ventilation and of rehabilitation problems. We wanted to see which clinical parameters can be used to identify patients with polyneuropathy in the intensive care. In a prospective study during 18 months, mechanically ventilated patients underwent serial neurological and EMG investigations in the general intensive care unit of a large community hospital. Fifty patients under 75 years old were studied who were on the respirator for more than 7 days. Using simple criteria, both a provisional clinical and an EMG diagnosis were made with regard to polyneuropathy during the second and fourth week and the second month of mechanical ventilation. After the intensive care period, 34 surviving patients were also given a final clinical diagnosis which was compared to earlier EMG conclusions. Even with crude criteria, such as the presence of either paresis or areflexia, maximal sensitivity of the provisional clinical judgement was only 60% as compared to concurrent EMG diagnosed polyneuropathy. EMG investigations in the intensive care, however, did not identify two out of 10 patients with a final clinical diagnosis of polyneuropathy. Thus, neurological examination is an insufficient screening method for polyneuropathy in intensive care. EMG has a fair diagnostic yield but one should realize that it is not an infallible gold standard.

Critical illness polyneuropathy in multiple organ dysfunction syndrome and weaning from the ventilator.

BACKGROUND: Acute axonal polyneuropathy has been found in patients with multiple organ dysfunction syndrome. This 'critical illness polyneuropathy' (CIP) has been associated with difficult weaning from the ventilator in retrospective studies. OBJECTIVE: To test the hypothesis that CIP is related to the degree and number of organ dysfunctions, and to weaning problems. DESIGN: Prospective study of 18 months. SETTING: A multidisciplinary intensive care unit in a general hospital SUBJECTS: Thirty-eight patients under 75 years of age who had been mechanically ventilated for more than 7 days, without previous signs of or risk factors for polyneuropathy. MEASURES: Organ dysfunctions were quantified using a dynamic scoring system (0-12 points). Electromyography studies were performed during mechanical ventilation to identify patients with and without CIP. RESULTS: CIP was present in 18 out of 38 patients and associated with an increased organ dysfunction score (5.3 +/- 1.8 vs. 3.6 +/- 1.5; p = 0.003) and number of organs involved [median (range): 4 (3-5) vs. 2 (1-4); p = 0.009], in particular cardiovascular (p = 0.003), renal (p = 0.04), and hematopoietic failure (p = 0.04). Patients with polyneuropathy were ventilated longer, but this was not clearly due to more difficult weaning [median: 16.5 (1-48) vs. 9.5 (1-38) days; p = 0.26]. Polyneuropathy was present in 2 of 4 patients with normal weaning. CONCLUSIONS: Axonal polyneuropathy is related to the severity of multiple-organ-dysfunction syndrome. Its presence does not necessarily implicate difficult weaning from artificial ventilation.

The role of polyneuropathy in motor convalescence after prolonged mechanical ventilation.

OBJECTIVE: To test the hypothesis that prolonged motor recovery after long-term ventilation may be due to polyneuropathy and can be foreseen at an early stage by electromyography (EMG). DESIGN: Cohort study with an entry period of 18 months. Polyneuropathy was identified by EMG studies in the intensive care unit (ICU). During a 1-year follow-up, amount of time was recorded to reach a rehabilitation end point. SETTING: The general ICU of a community hospital. PATIENTS: Fifty patients younger than 75 years who were receiving mechanical ventilation for more than 7 days. MAIN OUTCOME MEASURES: A rehabilitation end point was defined as return of normal muscle strength and ability to walk 50 m independently. RESULTS: In 29 of 50 patients, an EMG diagnosis of polyneuropathy was made in the ICU. Patients with polyneuropathy had a higher mortality in the ICU (14 vs 4; P = .03), probably related to multiple organ failure (22 vs 11; P = .08) or aminoglycoside treatment of suspected gram-negative sepsis (17 vs 4; P = .05). Rehabilitation was more prolonged in 12 patients with polyneuropathy than in 12 without polyneuropathy (P = .001). Of nine patients with delays beyond 4 weeks, eight had polyneuropathy, five of whom had persistent motor handicap after 1 year. In particular, axonal polyneuropathy with conduction slowing on EMG indicated a poor prognosis. CONCLUSIONS: Polyneuropathy in the critically ill is related to multiple organ failure and gram-negative sepsis, is associated with higher mortality, and causes important rehabilitation problems. EMG recordings in the ICU can identify patients at risk.

H reflexes as a measure for uremic polyneuropathy. A longitudinal study in patients treated with dialysis or renal transplantation.

Assessment of peripheral nerve function in end stage uremia by clinical and conventional nerve conduction velocity studies was compared to that using H reflex measurements. The latter proved to be the most sensitive technique. The results of the test correlated well with clinical and with other neuro-physiological measures. Nerve function as evaluated by H reflexes remained stable during the first 2 years of dialysis, but deteriorated later on. H reflex latencies shortened after renal transplantation. The results of H reflex measurements did not correlate with biochemical parameters, which makes the test a less attractive overall measure for the efficiency of therapy in uremia. In the follow-up of patients under treatment for uremic polyneuropathy, however, recording of H reflexes provides an important measure.

Sex differences in age regression parameters of healthy adults--normative data and practical implications.

After appropriate transformations age regression parameters for relative band power values were determined in two groups of normal subjects (94 men and 80 women) between 20 and 70 years of age. Four homologous bipolar derivations over each hemisphere were considered. For most regression equations significant sex differences were found for the intercept values; a sex difference for the regression coefficient was only present for the temporal theta power. The use of patient and control groups composed solely of subjects of the same sex can be indicated when studying groups of subjects with minor qEEG disturbances, an example of which is given.

Electroencephalographic studies in workers exposed to solvents or pesticides.

The qEEG was studied in groups of young and old workers exposed to solvents (house and industrial painters) and in a group of workers exposed to pesticides. Three methods were used: a quantified visual scoring system, the neurometrics method and a multivariate analysis of mean frequencies. Using the visual assessment as well as the neurometrics method, the older painters showed more abnormalities than the younger painters and the pesticide exposed workers. The "profile" of abnormalities differed in all 3 groups. Changes of the mean spectral frequencies were mainly found in the subjects exposed to pesticides. In this study we concluded that the neurometrics method can be useful in neurotoxicological studies. With this technique minor changes in electrocortical function can be detected in seemingly normal workers. However, frequency parameters should be added to the power measures which are usually studied.

Encephalopathy in patients on continuous ambulatory peritoneal dialysis and patients on chronic haemodialysis.

A group of 121 patients, 22 with a preterminal chronic renal insufficiency (PCRI), 74 on chronic haemodialysis (CHD), and 25 on continuous ambulatory peritoneal dialysis (CAPD), was evaluated by means of neurophysiological and neuropsychological studies to detect signs of central nervous system dysfunction. CHD patients were studied the day before dialysis treatment. In each patient the neurophysiological and neuropsychological studies were performed on the same day. The same overall result emerged from the neurophysiological and neuropsychological studies: all three patient groups showed significant deviations from the values obtained from a healthy reference group, whereas no differences were found between the three patient groups. Biochemical variables (a.o. PTH, Al, PO4) showed inconsistent or only minor correlations with the encephalopathic parameters. Apparently traditional biochemical variables are not a reliable measure to safeguard renal patients from neurotoxic damage. With respect to central nervous system dysfunction CAPD appears to be as 'safe' as CHD.

Neurometrics in cerebral ischemia and uremic encephalopathy.

The neurometric method as introduced by John was used to study three groups of patients with cerebral ischemia, three groups of patients with renal disease and an additional normal control group. The traditional neurometric approach was slightly modified: relative band power values were not expressed as a percentage of the total power per derivation but as a percentage of the "global power"; frequency matrices were used in addition to power matrices. From the study of the three groups of patients with one-sided supratentorial ischemia it appeared that sensitivity and specificity are completely satisfactory when using neurometrics in patients with severe ischemia in the middle cerebral artery territory studied within 48 hours of the onset of the stroke. However, in ischemia patients with less pronounced clinical signs and especially in patients without persistent neurological deficit the sensitivity is much lower. In studying dialysed and non-dialysed renal patients signs of an (often subclinical) encephalopathy could be detected in approximately 37% of all patients. Follow-up studies of the ischemia patients and the renal patients over a period of several years revealed a parallelism between clinical scores and qEEG scores in the ischemia patients; almost all qEEG improvement occurred in the first three months after the stroke. The qEEG profile of the groups of dialysed patients tended to be more or less stable over a period of several years.

Histopathological evaluation of oesophageal carcinoma: the significance of venous invasion.

Follow-up data on 115 patients who had undergone surgical resection for oesophageal carcinoma were analysed. Histological sections were reviewed for tumour classification, grading and staging, and special stains were used to detect venous invasion. The effect of various factors on survival was statistically analysed using Cox's proportional hazards regression model. In this multivariate analysis lymph node metastasis was the most important variable in the assessment of survival (improvement chi 2 = 7.43, P = 0.006). Venous invasion, which was demonstrated with a frequency of 76.5 per cent (mostly intramural) was the second most important prognostic factor (improvement chi 2 = 2.86, P = 0.09). The relative risk for the presence of both variables was rather modest (3.09).

Does compliance predict ventricular reduction after shunting for normal pressure hydrocephalus.

Ventricular reduction after shunting for normal pressure hydrocephalus (NPH) was classified on the basis of magnitude and rate of reduction in 35 adult patients. Brain compliance and resistance to outflow of cerebrospinal fluid (RCSF) were determined before shunting. Rapid and marked ventricular reduction (n = 11) was associated with a significantly lower compliance than slow and moderate to marked (n = 16) or minimal to mild (n = 8) reduction. Otherwise ventricular size before as well as after shunting did not correlate with compliance or RCSF. It is concluded that both rate and magnitude of ventricular reduction after shunting for NPH vary widely. Reduced compliance seems to be the best predictor of rapid and marked reduction.

Relationship between compliance and resistance to outflow of CSF in adult hydrocephalus.

Resistance to outflow of cerebrospinal fluid (Rcsf) was determined by constant flow infusions and pressure-volume index (PVI) using bolus infusions in 114 patients with various types of hydrocephalus. A clear correlation was found between PVI and Rcsf and, to a lesser degree, between these two parameters and baseline pressure. The PVI was not related to patient's age, duration of disease, type of hydrocephalus, or ventricular size, indicating that the relationship between PVI and Rcsf was genuine and not caused by patient selection. It is concluded that, in adult hydrocephalus, compliance is not an independent parameter but chiefly determined by Rcsf.

Long-term clinical and neurophysiological effects of reconstructive vascular surgery for cerebral ischemia.

In a series of patients with unilateral supratentorial ischemia, clinical scores and parameters derived from computer analysis of the EEG and from measurement of the CBF were determined in the first several weeks after the stroke. Seventeen of these patients underwent a carotid-endarterectomy and 15 a STA-MCA bypass operation. Matched control patients were selected from the remaining cases. All patients, including the controls, were eligible for vascular surgery. The measurements were repeated respectively 3 months and 3 years after the first examination. Clinical improvement occurred in all groups. The degree of these clinical changes was similar for operated and non operated cases. EEG changes indicated more improvement in the cases without surgery. Finally, the CBF was remarkably stable in all patients. The overall effects of reconstructive vascular surgery on the recovery after cerebral ischemia appeared to be negligible.

Recovery from cerebral ischaemia. EEG, cerebral blood flow and clinical symptomatology in the first three years after a stroke.

In 43 patients suffering from unilateral supratentorial ischaemia the changes over an interval of 3 years in clinical score, quantified EEG (using the neurometric method) and CBF (Xenon inhalation method) were studied. The patients were examined 3 times: shortly after the onset of ischaemia and respectively 3 and 36 months after this first measurement. Three patients died from causes not related to cerebral ischaemia. In the surviving patients the EEG and clinical score improved, often dramatically; the CBF values did not change significantly. Most of the changes occurred in the first 3 months after the stroke. For the evaluation of the prognostic value of the various parameters, 2 sub-groups of patients with different outcome but comparable initial clinical scores were studied. A persistent neurological deficit was predicted by a low CBF at the first measurement. The neurometric parameters obtained from the initial EEG had no value in this respect.

Follow-up of 146 children with epilepsy after withdrawal of antiepileptic therapy.

The relapse rate after discontinuation of antiepileptic drug treatment was investigated in 146 children with epilepsy, in whom medication was withdrawn according to a predesigned protocol, after a seizure-free period of at least 2 years and normalization of the EEG. The cumulative probability of remaining seizure-free in this series was 74.5%. Three-quarters of the relapses occurred during the withdrawal period and in the 2 years thereafter. From multivariate analysis, the factors indicating a significantly higher relapse risk were seizures with a known cause and female sex. In primary generalized epilepsy, no factor significantly increased the likelihood of a recurrence. In partial epilepsy, significant factors predictive of recurrence were the presence of a neurological deficit (focal neurological signs and/or mental retardation), female sex, a positive family history for epilepsy, and the number of drugs necessary for control of the seizures. The present results are compared with the available literature data. It is argued that using multivariate analysis after elimination of EEG variables uncovers significant clinical predictive factors that in other studies may have remained hidden. Finally, it is argued that statistical analysis may be used to enable the clinician to predict the likelihood of recurrence in individual children with a given set of relevant predictive factors.

Reduction of ventricular size after shunting for normal pressure hydrocephalus related to CSF dynamics before shunting.

Reduction of ventricular size was determined by repeated computed tomography in 30 adult patients shunted for normal pressure hydrocephalus (NPH) and related to the pressure-volume index (PVI) and resistance to outflow of cerebrospinal fluid (Rcsf) measured before shunting. Rapid and marked reduction of ventricular size (n = 10) was associated with a significantly lower PVI than slow and moderate to marked (n = 13) or minimal to mild reduction (n = 7). Otherwise no relationship could be found between the reduction of ventricular size and PVI or Rcsf. It is concluded that both rate and magnitude of reduction of ventricular size after shunting for NPH are extremely variable. High brain elasticity seems to be the best predictor of rapid and marked reduction.

The effect of reconstructive vascular surgery on clinical status, quantitative EEG and cerebral blood flow in patients with cerebral ischaemia. A three month follow-up study in operated and unoperated stroke patients.

Follow-up studies over a period of 3 months were carried out on 100 patients with a unilateral ischaemia in the territory of the middle cerebral artery. Twenty-six patients underwent an STA-MCA bypass operation and 23 patients, a carotid endarterectomy. Fifty-one unoperated patients served as a reference group. A clinical examination, quantitative electroencephalogram (qEEG) and cerebral blood flow study (CBF) were performed before, 2 weeks after and 3 months after surgery. In the unoperated patients these examinations were carried out shortly after admission, 3 weeks later and 3 months thereafter. In the unoperated group, a highly significant improvement of clinical score and qEEG was found, but there were no changes in CBF values. The bypass patients showed a transient deterioration of clinical score and qEEG after surgery. Further, over the 3 month post-operative period, the bypass patients and the endarterectomy patients showed no improvement in CBF and qEEG. Thus, a beneficial effect of reconstructive surgery over the period studied could not be demonstrated.

The use of neurometrics in the study of patients with cerebral ischaemia.

The 'neurometric' method, as developed by John, was used for the study of patients with one-sided supratentorial ischaemia. The results of a reference group of 64 normal volunteers were compared with those of a group of 94 patients. This patient group included 54 patients with permanent neurological deficit (completed stroke or partial non-progressive stroke) and 40 patients with transient neurological symptoms (reversible ischaemic neurological deficit or transient ischaemic attacks). In 90% of all patients the neurometric method indicated that the EEG had to be considered as abnormal (compared with 3% of false positives in the reference group). A significant overall asymmetry was found in 82% of all patients compared with 2% in the reference group. During the follow-up period of 3 months there was a significant improvement of the EEG (as indicated by 3 neurometric parameters) as well as an improvement in clinical condition. In 57.5% of the EEGs, both the neurometric score and the visual assessment of the EEG indicated that some abnormality was present. In 6.6% of the cases both methods failed to indicate any abnormality. In 34.0% the neurometrics method revealed an abnormality in the EEG which was not found by visual assessment. In only 1.9% of the patients did visual assessment suggest abnormalities which could not be confirmed by neurometrics. In the group of EEGs which were considered as normal by visual assessment, the neurometrics method revealed abnormalities in 84%. The neurometric method is at the moment the most sensitive approach for detecting abnormalities in the EEG of patients with unilateral cerebral ischaemia. However, the method seems not very accurate for lateralization or localization of the lesions.

CSF outflow resistance and pressure-volume index determined by steady-state and bolus infusions.

Intraventricular or lumbar CSF pressure was measured in 58 adult hydrocephalic patients. CSF outflow resistance (Rcsf) and pressure-volume index (PVI) were determined by steady-state and bolus infusion techniques, using mathematical models with and without a constant term. Comparison of the various Rcsf and PVI values indicates that the most reliable Rcsf is obtained by steady-state infusion. The best approximation of the PVI is obtained by bolus infusions, provided the pressure decay curve is excluded. Mathematically a model with a constant term is to be preferred.

Comparison of ventricular steady-state infusion with bolus infusion and pressure recording for differentiating between arrested and non-arrested hydrocephalus.

In 6 years 26 adult patients with chronic communicating or non-communicating hydrocephalus underwent ventricular fluid pressure (VFP) recording, including intraventricular steady-state and bolus infusion tests. Patients were treated with a shunt when steady-state infusion yielded a csf outflow resistance (Rcsfs) greater than 10 mm Hg/ml/min; the success rate was 83%. The main purpose of the study was to compare Rcsfs with outflow resistance obtained by bolus infusions (Rcsfb), pressure-volume index (PVI) and VFP. Rcsfs was higher than Rcsfb, particularly when resistance was high and the degree of disturbance of csf dynamics was reflected by Rcsfs better than by Rcsfb. The PVI showed a roughly inverse relationship with the Rcsfs but was not helpful in differentiating arrested from non-arrested hydrocephalus. Rcsfs and VFP correlated better than expected. A high Rcsfs was associated with an elevated VFP and a normal Rcsfs with a normal VFP. VFP only varied when Rcsfs exhibited a mild to moderate increase. It is concluded that steady-state infusion remains the most reliable method for the prediction of the result of shunting. We recommend shunting when Rcsfs is greater than 10 mm Hg/ml/min. Bolus infusions provide valuable data on brain elastance and additional information on csf outflow resistance. VFP recording is certainly worthwhile because infusion tests can be omitted when VFP is clearly elevated and useful information is obtained when Rcsf is borderline.